1. Technical Field
The subject invention relates generally to cylinder blocks for internal combustion engines, and more particularly to such cylinder blocks having cylinder liners which are metallurgically bonded to the block.
2. Description of the Prior Art
Aluminum cylinder blocks for internal combustion engines are typically provided with cylinder liners made of cast iron or other suitable material for providing a high wear-resistant surface to the cylinder walls of the cylinder block. In order to prevent the liners from moving and rendering the engine inoperable, it is important that the cylinder liners be securely joined to the cylinder block.
One common method for joining the liners to the block is to form a mechanical interference or interlock between the liner and the block. One method involves pressing the liners into the engine block with an interference fit, relying on the friction between the liner and the block to hold the liner in place. Another method is to cast the cylinder block around the cylinder liners to form such a mechanical interlock or interference. Although these types of liners have enjoyed some commercial success, they are deficient in that mechanically joined liners tend to loosen over time due to the continuous thermal cycling of the engine and the different co-efficiency of expansion of the liner and cylinder block materials. An example of such a liner is disclosed in the U.S. Pat. No. 3,069,209 to Bauer, granted Dec. 18, 1962.
Another method for joining the liner to the cylinder block is to metallurgically bond the liner to the block. The methods known thus far involve coating the outer surfaces of preformed liners with a low melting point metal material and then positioning these coated liners in a mold and casting the cylinder block around the coated liners, which causes the coating to melt an alloy with the block and liner material to form a metallurgical bond between the liners and the block. Examples of such cast-in-place methods are disclosed in the U.S. Pat. Nos. 1,710,136 to Angle et al, granted Apr. 23, 1929; 3,165,983, granted Jan. 19, 1965 and 3,276,082 granted Oct. 4, 1966, both to Thomas, and 5,005,469, granted Apr. 9, 1991 to Ohta. With all of these cast-in-place lining methods, special care must be taken to properly position the liners within the casting mold prior to casting.
Thus, the methods available in today's technology are either inadequate, in the case of mechanical bonded liners, or require special fixturing, in the case of cast-in place metallurgically bonded liners, in order to properly locate these liners within the resultant cast cylinder block.